This is the problem. It was the problem two years ago at the second World Urban Forum in Barcelona, and more than likely it will be the problem at the fourth in Nanjing in 2008.

Clearly, the issues the forum was discussing are of phenomenal importance.

The human race simply cannot go on living the way it does - that much is certain.

And yet in terms of taking serious action to address this, this forum had nothing to offer - no announcements, no firm commitments, and certainly no cash.

What was left were speeches - often undeniably heartfelt - and the endless calls for power to be devolved.

Real ideas

And yet, often tucked away in a dark corner of the exposition, there were some real, practical, and actionable ideas here.

And, even better, they were ideas that really could make a difference.

London's congestion charge has been widely judged a success

Two particularly striking ones were Scandinavian.

For example, there was the Swedish town that virtually powers itself, including its cars, on the biogas waste from the local slaughterhouse.

Indeed, the cities of the world could do a lot worse in driving themselves towards sustainability by copying the Swedish examples on display here. Many, including London, Toronto and Cork, are doing just that.

Interestingly, Sweden has particularly strong local government, with Swedish income taxes going to the municipal halls rather to the central government.

Which perhaps, after all, goes to show the merit in the calls for devolved power.

Car-free city

On a much smaller scale, but just as intriguing, were some designs by a student from Oslo which showed how street furniture could be used to help the homeless - by, for example, enclosing the space between two benches to make a sleeping shelter.

Adapting park benches into shelters could help the homeless

Perhaps it would be a touch idealistic to expect such an arrangement to go unabused, but at least it was a real idea that could be put into action.

Meanwhile, from a completely different part of the world, the mayor of the Colombian capital, Bogota, told of just exactly what could be done with the real will to meet some of challenges of making cities sustainable.

Faced with calls to upgrade and expand the city's road network, he argued such a move was unwarranted, as car usage is relatively low - only around 12% of the capital's people regularly drive.

Instead, funds were put into a "car free city" and as a result, Bogota now has more cycle paths - 300km of them - than almost any other city in the world.

Here are grounds for optimism indeed.

And if the urban planners of the world go away and use these examples in their own cities, then the World Urban Forum will have been worthwhile.

But nothing happened in Vancouver that will make them do so - and until there is, the suspicion will remain that these forums are much more about talk than action.